Refreshed macos install article

[mikefrobbins]

PR Summary

Refreshed macOS install article. Updated the flow or the article.

PR Checklist

• Descriptive Title: This PR's title is a synopsis of the changes it proposes.
• Summary: This PR's summary describes the scope and intent of the change.
• Contributor's Guide: I have read the contributor's guide.
• Style: This PR adheres to the style guide.

[sdwheeler]

LGTM

[learn-build-service-prod]

Learn Build status updates of commit 2366250:

✅ Validation status: passed

File	Status	Preview URL	Details
reference/docs-conceptual/install/Installing-PowerShell-on-macOS.md	✅Succeeded	View (>=powershell-5.1)

For more details, please refer to the build report.